Russia’s war in Ukraine and the associated energy challenges have heightened the focus on energy security. Over the past three years, as part of a larger project on Europe & Eurasia (E&E), AidData has developed an Energy Security Index (ESI) for the region. The ESI tracks energy security trends over two decades to help policymakers target their assistance and monitor results over time, with comparability across countries. This policy brief presents results for the ESI in 17 countries in four sub-regions: Eastern Europe, the Balkans, the Caucasus, and Central Asia. A hallmark of AidData's ESI is the ability to dig deeply into the components of energy security, providing insights into: (1) the strengths and weaknesses of energy policies, governance, supply, and infrastructure; (2) the risks to the energy systems of countries; and (3) the resilience of those systems to political, economic, technological, and environmental shocks. The ultimate objective is to bolster energy security by improving how areas of opportunity can be diagnosed in specific countries and across the region.